correct as is Right DDI controls HUD & MPCD power

[norman99]

Hi, I'm not sure if this is correct or not. It seems the right DDI's OFF/NIGHT/DAY switch also controls power to the HUD and MPCD. Not really noticeable on startup, as most people switch the DDIs on first, but it's noticeable on shutdown if the same order is used.

 

I've searched through as many documents as I could find DCS, NATOPS etc, but I can find no mention of HUD and MPCD electrical power coming via the right DDI, and requiring it powered on first.

 

In the video below, the left engine is already shutdown. As you can see, switching the right DDI off also affects the HUD and MPCD. Their own individual switches still work correctly, but they require the right DDI to be powered on to function.

 

 

Edited March 10, 2021 by norman99

[Swift.]

So I did a little digging, it looks like:

The MPCD is driven by the Left DDI for its menu selectable formats, which I assume means the LDDI must be powered for it to work.

 

The HUD is driven by either the Left or Right DDI symbology generators, so I assume that means it can be driven by either display being powered.

 

My understanding then, is that,
LDDI-Off and RDDI-On = MPCD-Off and HUD-On
LDDI-On and RDDI-Off = MPCD-ON and HUD-On
LDDI-Off and RDDI-Off = MPCD-Off and HUD-Off

[norman99]

I saw those descriptions in the NATOPS manual as well. What it dosen't explain clearly, is whether the OFF/NIGHT/DAY switch of the DDI controls power to the display generators as well as the DDI screens. If so, than your examples above shout be correct.

 

If the switches simply control the DDIs only, and the display generators are always powered, then they shouldn't affect HUD and MPCD operation.

 

Either way, the current implementation is incorrect re the MPCD as it's currently controlled by the right DDI, not the left.

[mongo52]

HUD is driven by RDDI MPCD is driven by LDDI IRL. 

[Swift.]

16 minutes ago, norman99 said:

I saw those descriptions in the NATOPS manual as well. What it dosen't explain clearly, is whether the OFF/NIGHT/DAY switch of the DDI controls power to the display generators as well as the DDI screens. If so, than your examples above shout be correct.

 

If the switches simply control the DDIs only, and the display generators are always powered, then they shouldn't affect HUD and MPCD operation.

 

Either way, the current implementation is incorrect re the MPCD as it's currently controlled by the right DDI, not the left.

Correct but incorrect. In DCS right now, both the HUD and the MPCD are driven by either the Right or the Left DDI, having one powered is enough. 

[norman99]

Ahh, I didn't think to test switching off the DDIs in the other order, so I didn't know either currently powered the MPCD. 

Edited March 11, 2021 by norman99